The present invention relates to lift truck carriages which selectively shift a load transversely while the load is supported by a load-handling implement such as a pair of forks or a clamp. More particularly, the present invention is directed to improvements to such carriages for reducing their susceptibility to structural failure while compatibly maximizing operator visibility.
Lift truck sideshifting carriages have primarily been produced in two different forms. One form is an integral sideshifting carriage which has a built-in sideshifting structure and can mount a load-handling implement only on the sideshifting structure. The other form is a nonintegral sideshifting carriage which has a sideshifting structure detachably mounted thereon, and can mount a load-handling implement either with or without the sideshifting structure. In both forms of sideshifting carriage, transversely-extending, vertically-spaced upper and lower slide guides slidably support a sideshifting frame upon which the load and load-handling implement are supported in cantilevered fashion. The load is shifted transversely by a sideshifting motor, such as a hydraulic piston and cylinder assembly, which slides the sideshifting frame transversely along the slide-guides. The transversely-extending upper slide guide is subjected to high, fluctuating beam loading in a horizontal forward direction, to counteract the weight of the forwardly-cantilevered load. Such loading severely stresses the joints by which the slide guide is attached to a pair of transversely-spaced vertical side plates which movably engage the mast of the lift truck for lifting and lowering of the load, tending to cause fatigue failures at the joints.
The stresses from such cantilevered loading are increased as the height of the upper slide guide relative to the lower slide guide is decreased, because the vertical lever arm between the slide guides is decreased. Nevertheless, it has been common design practice to minimize the height of the upper slide guide to increase operator forward visibility over the top of the sideshifting frame, even though this decreases the visibility between the upper and lower slide guides because of the reduced space between them. These stress and visibility problems are particularly common in integral sideshifting carriages, where the sideshifting frame protrudes upwardly a significant distance above the upper slide guide to minimize forward protrusion of the sideshifting frame and thereby maximize the load-carrying capacity of counterbalanced lift trucks. The problems are further aggravated in integral sideshifting carriages by the common practice of enclosing a sideshifting motor within the upper slide guide, thereby dictating the size and shape of the slide guide and making it difficult to optimize its strength and size.
Accordingly, what is needed is an improved sideshifting carriage having an upper slide guide, sideshifting frame and sideshifting motor arranged so as to maximize strength and operator visibility compatibly.
The present invention satisfies the foregoing need by providing a unique upper slide guide with an upwardly-protruding lip for slidably supporting the slide of a sideshifting frame, and a transversely-extending reinforcing portion which protrudes forwardly from beneath the forwardly-facing surface of the lip and extends throughout at least a major portion of the transverse length of the slide guide. A sideshifting motor engages the sideshifting frame so as to move the frame transversely with respect to the slide guide.
According to one independent preferred aspect of the invention, the sideshifting motor is preferably mounted beneath the reinforcing portion of the slide guide externally of the reinforcing portion.
According to another preferred independent aspect of the invention, the forwardly-protruding reinforcing portion of the slide guide and the upwardly-protruding lip of the slide guide are formed monolithically and homogeneously as a single member.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description, taken in conjunction with the accompanying drawings.